U.S. patent number 8,774,299 [Application Number 13/757,695] was granted by the patent office on 2014-07-08 for transmitting spread signal in communication system.
This patent grant is currently assigned to LG Electronics Inc.. The grantee listed for this patent is LG Electronics Inc.. Invention is credited to Joon Kui Ahn, Ki Jun Kim, Dae Won Lee, Jung Hoon Lee, Dong Wook Roh.
United States Patent |
8,774,299 |
Lee , et al. |
July 8, 2014 |
Transmitting spread signal in communication system
Abstract
The present invention provides for transmitting a spread signal
in a mobile communication system. The present invention includes
spreading a signal using a plurality of spreading codes, wherein
the plurality of spreading codes have a spreading factor,
multiplexing the spread signal by code division multiplexing,
transmitting the multiplexed signal via a plurality of neighboring
frequency resources of one OFDM symbol of a first antenna set, and
transmitting the same multiplexed signal via a plurality of
neighboring frequency resources of one OFDM symbol of a second
antenna set.
Inventors: |
Lee; Jung Hoon (Anyang-si,
KR), Kim; Ki Jun (Anyang-si, KR), Roh; Dong
Wook (Anyang-si, KR), Lee; Dae Won (Anyang-si,
KR), Ahn; Joon Kui (Anyang-si, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
LG Electronics Inc. |
Seoul |
N/A |
KR |
|
|
Assignee: |
LG Electronics Inc. (Seoul,
KR)
|
Family
ID: |
40368872 |
Appl.
No.: |
13/757,695 |
Filed: |
February 1, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130148697 A1 |
Jun 13, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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13045455 |
Mar 10, 2011 |
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12139254 |
May 31, 2011 |
7953169 |
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60943783 |
Jun 13, 2007 |
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60955019 |
Aug 9, 2007 |
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60976487 |
Oct 1, 2007 |
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60982435 |
Oct 25, 2007 |
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60983234 |
Oct 29, 2007 |
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Foreign Application Priority Data
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Nov 29, 2007 [KR] |
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10-2007-122986 |
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Current U.S.
Class: |
375/260 |
Current CPC
Class: |
H04B
7/0678 (20130101); H04B 7/068 (20130101); H04L
5/0021 (20130101); H04B 1/707 (20130101); H04L
5/0055 (20130101); H04L 5/0023 (20130101); H04J
13/00 (20130101); H04L 1/0606 (20130101); H04J
13/16 (20130101); H04L 27/2601 (20130101) |
Current International
Class: |
H04L
27/28 (20060101) |
Field of
Search: |
;375/230,259,260,267
;370/342 |
References Cited
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Primary Examiner: Burd; Kevin M
Attorney, Agent or Firm: Lee, Hong, Degerman, Kang &
Waimey
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 13/045,455, filed on Mar. 10, 2011, which is a continuation of
U.S. patent application Ser. No. 12/139,254, filed on Jun. 13,
2008, now U.S. Pat. No. 7,953,169, which claims the benefit of
earlier filing date and right of priority to Korean Patent
Application No. 10-2007-122986, filed on Nov. 29, 2007, and also
claims the benefit of U.S. Provisional Application Ser. Nos.
60/943,783, filed on Jun. 13, 2007, 60/955,019, filed on Aug. 9,
2007, 60/976,487, filed on Oct. 1, 2007, 60/982,435, filed on Oct.
25, 2007, and 60/983,234, filed on Oct. 29, 2007, the contents of
which are all hereby incorporated by reference herein in their
entirety.
Claims
What is claimed is:
1. A method of communicating in a mobile communication system
comprising a user equipment (UE) and a base station (BS), the
method comprising: transmitting, by the BS, a first signal
including first spread Acknowledqement/Negative acknowledgement
(ACK/NACK) information in an orthogonal frequency division
multiplexing (OFDM) symbol, wherein the first spread ACK/NACK
information is in a first antenna set in a form as shown in an
upper half of Table 1; transmitting, by the BS, a second signal
including second spread ACK/NACK information in an OFDM symbol,
wherein the second spread ACK/NACK information is in a second
antenna set in a form as shown in a lower half of Table 1;
receiving, by the UE, a first signal including first spread
ACK/NACK information in an orthogonal frequency division
multiplexing (OFDM) symbol from the first antenna set of the BS;
receiving, by the UE, a second signal including second spread
ACK/NACK information in an OFDM symbol from the second antenna set
of the BS; de-spreading, by the UE, the first spread ACK/NACK
information for identifying the ACK/NACK information; and
de-spreading, by the UE, the second spread ACK/NACK information for
identifying the ACK/NACK information: TABLE-US-00001 TABLE 1 four
available neighboring subcarriers the first antenna A a.sub.1
a.sub.2 a.sub.3 a.sub.4 antenna set antenna B -a.sub.2* a.sub.1*
-a.sub.4* a.sub.3* the second antenna C b.sub.1 b.sub.2 b.sub.3
b.sub.4 antenna set antenna D -b.sub.2* b.sub.1* -b.sub.4*
b.sub.3*
wherein a.sub.1 to a.sub.4 are elements of the first spread
ACK/NACK information, b.sub.1 to b.sub.4 are elements of the second
spread ACK/NACK information, and the symbol * denotes a conjugate
operation, wherein the first spread ACK/NACK information and the
second spread ACK/NACK information carry identical ACK/NACK
information, and wherein the four available neighboring subcarriers
for the first spread ACK/NACK information are separated from the
four available neighboring subcarriers for the second spread
ACK/NACK information by a plurality of subcarriers in a frequency
domain.
2. The method of claim 1, wherein the four available neighboring
subcarriers for the first spread ACK/NACK information and the four
available neighboring subcarriers for the second spread ACK/NACK
information exist in different OFDM symbols.
3. The method of claim 1, further comprising: receiving, by the UE,
a third signal including third spread ACK/NACK information in an
OFDM symbol from the first antenna set of the BS; and de-spreading,
by the UE, the third spread ACK/NACK information for identifying
the ACK/NACK information, wherein the third spread ACK/NACK
information is in the first antenna set in a form as shown in Table
1 in which a.sub.1 to a.sub.4 are replaced with c.sub.1 to c.sub.4,
respectively, wherein c.sub.1 to c.sub.4 are elements of the third
spread ACK/NACK information, wherein the first spread ACK/NACK
information and the third spread ACK/NACK information carry
identical ACK/NACK information, and wherein the four available
neighboring subcarriers for the first spread ACK/NACK information
are separated from the four available neighboring subcarriers for
the third spread ACK/NACK information by a plurality of subcarriers
in a frequency domain.
4. The method of claim 1, wherein the antennas A and B are first
two contiguously numbered antennas, and the antennas C and D are
second two contiguously numbered antennas.
5. The method of claim 1, wherein the antennas A and B are
odd-numbered antennas, and the antennas C and D are even-numbered
antennas.
6. A mobile communication system including a user equipment (UE)
and a base station (BS), the BS comprising: a first radio frequency
unit configured to transmit a radio frequency signal; and a first
processor operably coupled to the first radio frequency unit and
configured to control the first radio frequency unit to: transmit a
first signal including first spread Acknowledgement/Negative
acknowledgement (ACK/NACK) information in an orthogonal frequency
division multiplexing (OFDM) symbol, the first spread ACK/NACK
information is in a first antenna set in a form as shown in an
upper half of Table 1; and transmit a second signal including
second spread ACK/NACK information in an OFDM symbol, the second
spread ACK/NACK information is in a second antenna set in a form as
shown in a lower half of Table 1; and the UE comprising: a second
radio frequency unit configured to transmit a radio frequency
signal; and a second processor operably coupled to the second radio
frequency unit and configured to: control the second radio
frequency unit to receive the first signal from the first antenna
set of the BS, control the second radio frequency unit to receive
the second signal from the second antenna set of the BS, de-spread
the first spread ACK/NACK information for identifying the ACK/NACK
information; and de-spread the second spread ACK/NACK information
for identifying the ACK/NACK information: TABLE-US-00002 TABLE 1
four available neighboring subcarriers the first antenna A a.sub.1
a.sub.2 a.sub.3 a.sub.4 antenna set antenna B -a.sub.2* a.sub.1*
-a.sub.4* a.sub.3* the second antenna C b.sub.1 b.sub.2 b.sub.3
b.sub.4 antenna set antenna D -b.sub.2* b.sub.1* -b.sub.4*
b.sub.3*
wherein a.sub.1 to a.sub.4 are elements of the first spread
ACK/NACK information, b.sub.1 to b.sub.4 are elements of the second
spread ACK/NACK information, and the symbol * denotes a conjugate
operation, wherein the first spread ACK/NACK information and the
second spread ACK/NACK information carry identical ACK/NACK
information, and wherein the four available neighboring subcarriers
for the first spread ACK/NACK information are separated from the
four available neighboring subcarriers for the second spread
ACK/NACK information by a plurality of subcarriers in a frequency
domain.
7. The mobile communication system of claim 6, wherein the four
available neighboring subcarriers for the first spread ACK/NACK
information and the four available neighboring subcarriers for the
second spread ACK/NACK information exit in different OFDM
symbols.
8. The mobile communication system of claim 6, wherein the second
processor is further configured to: control the second radio
frequency unit to receive a third signal including third spread
ACK/NACK information in an OFDM symbol from the first antenna set
of the BS; and de-spread the third spread ACK/NACK information for
identifying the ACK/NACK information, wherein the third spread
ACK/NACK information is in the first antenna set in a form as shown
in Table 1 in which a.sub.1 to a.sub.4 are replaced with c.sub.1 to
c.sub.4, respectively, wherein c.sub.1 to c.sub.4 are elements of
the third spread ACK/NACK information, wherein the first spread
ACK/NACK information and the third spread ACK/NACK information
carry identical ACK/NACK information, and wherein the four
available neighboring subcarriers for the first spread ACK/NACK
information are separated from the four available neighboring
subcarriers for the third spread ACK/NACK information by a
plurality of subcarriers in a frequency domain.
9. The mobile communication system of claim 6, wherein the antennas
A and B are first two contiguously numbered antennas, and the
antennas C and D are second two contiguously numbered antennas.
10. The mobile communication system of claim 6, wherein the
antennas A and B are odd-numbered antennas, and the antennas C and
D are even-numbered antennas.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication system, and more
particularly, to transmitting a spread signal in a communication
system.
2. Discussion of the Related Art
Recently, the demand for wireless communication services has risen
abruptly due to the generalization of information communication
services, the advent of various multimedia services and the
appearance of high-quality services. To actively cope with the
demand, a communication system's capacity should first be
increased. In order to do so, methods for finding new available
frequency bands and raising the efficiency of given resources in
wireless communication environments are considered.
Much effort and attention has been made to research and develop
multi-antenna technology. Here, diversity gain is obtained by
additionally securing a spatial area for resource utilization with
a plurality of antennas provided to a transceiver or raising
transmission capacity by transmitting data in parallel via each
antenna.
An example of a multi-antenna technology is a multiple input
multiple output (MIMO) scheme. The MIMO scheme indicates an antenna
system having multiple inputs and outputs, raises a quantity of
information by transmitting different information via each
transmitting antenna, and enhances reliability of transport
information using coding schemes such as STC (space-time coding),
STBC (space-time block coding), SFBC (space-frequency block coding)
and the like.
SUMMARY OF THE INVENTION
The present invention is directed to transmitting a spread signal
in a mobile communication system.
Additional features and advantages of the invention will be set
forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
To achieve these and other advantages and in accordance with the
purpose of the present invention, as embodied and broadly
described, the present invention is embodied in a method for
transmitting a spread signal in a mobile communication system, the
method comprising spreading a signal using a plurality of spreading
codes, wherein the plurality of spreading codes have a spreading
factor, multiplexing the spread signal by code division
multiplexing, transmitting the multiplexed signal via a plurality
of neighboring frequency resources of one OFDM symbol of a first
antenna set, and transmitting the same multiplexed signal via a
plurality of neighboring frequency resources of one OFDM symbol of
a second antenna set.
Preferably, the multiplexed signal is transmitted on four
neighboring frequency resources. Preferably, the spreading factor
is 4. Alternatively, the spreading factor is equal to the number of
neighboring frequency resources.
In one aspect of the present invention, the first antenna set is
space frequency block coded by applying a space frequency block
code to each neighboring pair of frequency resources of one OFDM
symbol, wherein the first antenna set comprises two antennas.
Moreover, the second antenna set is space frequency block coded by
applying a space frequency block code to each neighboring pair of
frequency resources of one OFDM symbol, wherein the second antenna
set comprises two antennas.
Preferably, the multiplexed signal transmitted via the first
antenna set and the multiplexed signal transmitted via the second
antenna set are transmitted via respectively different frequency
resources. Preferably, the multiplexed signal transmitted via the
first antenna set and the multiplexed signal transmitted via the
second antenna set are transmitted via respectively different OFDM
symbols.
In another aspect of the present invention, the multiplexed signal
is transmitted alternately by the first antenna set and second
antenna set via independent frequency resources repeatedly.
Preferably, the multiplexed signal is transmitted a total of 3
times using the first antenna set and second antenna set
alternately.
In one aspect of the present invention, the first antenna set
comprises a first antenna and a second antenna of a four-antenna
group, and the second antenna set comprises a third antenna and a
fourth antenna of the four-antenna group.
In another aspect of the present invention, the first antenna set
comprises a first antenna and a third antenna of a four-antenna
group, and the second antenna set comprises a second antenna and a
fourth antenna of the four-antenna group.
It is to be understood that both the foregoing general description
and the following detailed description of the present invention are
exemplary and explanatory and are intended to provide further
explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention. Features, elements, and aspects of
the invention that are referenced by the same numerals in different
figures represent the same, equivalent, or similar features,
elements, or aspects in accordance with one or more
embodiments.
FIG. 1 is a diagram illustrating an example of a method for
applying an SFBC/FSTD scheme in a communication system in
accordance with one embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 3 is a diagram illustrating an example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 4 is a diagram illustrating another example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 5 is a diagram illustrating an example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 6 is a diagram illustrating another example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 7 is a diagram illustrating an example of a method for
transmitting a spread signal via a plurality of OFDM symbols in
accordance with one embodiment of the present invention.
FIG. 8 is a diagram illustrating an example of a method for
transmitting a spread signal via a plurality of OFDM symbols in
accordance with one embodiment of the present invention, in which
an SFBC/FSTD scheme is applied to the spread signal.
FIG. 9 is a diagram illustrating an example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 10 is a diagram illustrating another example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 11 is a diagram illustrating another example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 12 is a diagram illustrating another example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present
invention.
FIG. 13 is a diagram illustrating an example of a method for
applying an SFBC/FSTD scheme to at least one spread signal in a
communication system in accordance with one embodiment of the
present invention.
FIG. 14 is a diagram illustrating an example of a method for
transmitting a spread signal in a mobile communication system in
accordance with one embodiment of the present invention.
FIG. 15 is a diagram illustrating an example of a method for
receiving a spread signal in a mobile communication system in
accordance with one embodiment of the present invention.
FIG. 16 is a diagram illustrating an example of a base station and
a user equipment in a mobile communication system in accordance
with one embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to transmitting a spread signal in a
wireless communication system.
Reference will now be made in detail to the preferred embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings. It is to be understood that the following
detailed description of the present invention is exemplary and
explanatory and is intended to provide further explanation of the
invention as claimed. The following detailed description includes
details to provide complete understanding of the present invention.
Yet, it is apparent to those skilled in the art that the present
invention can be embodied without those details. For instance,
predetermined terminologies are mainly used for the following
description, need not to be limited, and may have the same meaning
in case of being called arbitrary terminologies.
To avoid vagueness of the present invention, the structures or
devices known in public are omitted or depicted as a block diagram
and/or flowchart focused on core functions of the structures or
devices. Wherever possible, the same reference numbers will be used
throughout the drawings to refer to the same or like parts.
For the following embodiments, elements and features of the present
invention are combined in prescribed forms. Each of the elements or
features should be considered as selective unless there is separate
and explicit mention. Each of the elements or features can be
implemented without being combined with others. And, it is able to
construct an embodiment of the present invention by combining
partial elements and/or features of the present invention. The
order of operations explained in the following embodiments of the
present invention can be changed. Some partial configurations or
features of a prescribed embodiment can be included in another
embodiment and/or may be replaced by corresponding configurations
or features of another embodiment.
In this disclosure, embodiments of the present invention are
described mainly with reference to data transmitting and receiving
relations between a base station and a terminal. In this case, the
base station has a meaning of a terminal node of a network, which
directly performs communication with the terminal. In this
disclosure, a specific operation described as performed by a base
station can be carried out by an upper node of the base station.
Namely, it is understood that various operations carried out by a
network, which includes a plurality of network nodes including a
base station, for the communication with a terminal can be carried
out by the base station or other network nodes except the base
station. "Base station" can be replaced by such a terminology as a
fixed station, Node B, eNode B (eNB), access point and the like.
And, "terminal" can be replaced by such a terminology as UE (user
equipment), MS (mobile station), MSS (mobile subscriber station)
and the like.
FIG. 1 is a diagram illustrating an example of a method of applying
an SFBC/FSTD scheme in a wireless communication system, in
accordance with one embodiment of the present invention. In FIG. 1,
a method for obtaining 4-degree transmitting antenna diversity is
implemented using a plurality of transmitting antennas, e.g., four
downlink transmitting antennas of a communication system. Here, two
modulation signals transmitted via two adjacent subcarriers are
transmitted via a first antenna set including two antennas by
having space frequency block coding (SFBC) applied thereto. Two
SFBC-coded subcarrier sets are transmitted via two different
antenna sets each including two different antennas by having
frequency switching transmit diversity (FSTD) applied thereto. As a
result, a transmitting antenna diversity degree 4 can be
obtained.
Referring to FIG. 1, a single small box indicates a single
subcarrier transmitted via a single antenna. The letters "a", "b",
"c" and "d" represent modulation symbols modulated into signals
differing from each other. Moreover, functions f.sub.1(x),
f.sub.2(x), f.sub.3(x) and f.sub.4(x) indicate random SFBC
functions that are applied to maintain orthogonality between two
signals. These functions can be represented as in Equation
f.sub.1(x)=x,f.sub.2(x)=x,f.sub.3(x)=-x*,f.sub.4(x)=x [Equation
1]
Despite two signals being simultaneously transmitted via two
antennas through the random SFBC function applied to maintain
orthogonality between the two signals, a receiving side may be able
to obtain an original signal by decoding each of the two signals.
In particular, FIG. 1 shows a structure that SFBC and FSTD
transmitted in downlink within a random time unit is repeated. By
applying a simple reception algorithm that the same SFBC decoding
and FSTD decoding are repeated in a receiving side through the
structure of SFBC and FSTD repeating transmissions, decoding
complexity is reduced and decoding efficiency is raised.
In the example shown in FIG. 1, modulated symbol sets (a, b), (c,
d), (e, f) and (g, h) become an SFBC-coded set, respectively. FIG.
1 shows that subcarriers having SFBC/FSTD applied thereto are
consecutive. However, the subcarriers having SFBC/FSTD applied
thereto may not necessarily be consecutive in a frequency domain.
For instance, a subcarrier carrying a pilot signal can exist
between SFBC/FSTD applied subcarriers. Yet, two subcarriers
constructing an SFBC coded set are preferably adjacent to each
other in a frequency domain so that wireless channel environments
covered by a single antenna for two subcarriers can become similar
to each other. Hence, when SFBC decoding is performed by a
receiving side, it is able to minimize interference mutually
affecting the two signals.
In accordance with one embodiment of the present invention, an
SFBC/FSTD scheme may be applied to a spread signal sequence. In a
manner of spreading a single signal into a plurality of subcarriers
through (pseudo) orthogonal code in a downlink transmission, a
plurality of spread signals may be transmitted by a code division
multiplexing (CDM) scheme.
For example, when attempting to transmit different signals "a" and
"b", if the two signals are to be CDM-transmitted by being spread
by a spreading factor (SF) 2, the signal a and the signal b are
transformed into spread signal sequences (ac.sub.11, ac.sub.21) and
(bc.sub.12, bc.sub.22) using (pseudo) orthogonal spreading codes of
two chip lengths (c.sub.11, c.sub.21) and (c.sub.12, c.sub.22),
respectively. The spread signal sequences are modulated by adding
ac.sub.11+.bc.sub.12 and ac.sub.21+bc.sub.22 to two subcarriers,
respectively. Namely, ac.sub.11+.bc.sub.12 and ac.sub.21+bc.sub.22
become modulated symbols, respectively. For clarity and
convenience, the spread signal sequence resulting from spreading
the signal a by SF=N is denoted as a.sub.1, a.sub.2, . . . ,
a.sub.N.
FIG. 2 is a diagram illustrating an example of a method of applying
an SFBC/FSTD scheme to a spread signal in a communication system,
in accordance with one embodiment of the present invention. In
order to decode a signal spread over a plurality of subcarriers by
despreading in a receiving side, as mentioned in the foregoing
description, it is preferable that each chip of a received spread
signal sequence undergo a similar wireless channel response. In
FIG. 2, four different signals a, b, c and d are spread by SF=4 and
the spread signals are transmitted by SFBC/FSTD through four
subcarriers explained in the foregoing description of FIG. 1.
Assuming that the function explained for the example in Equation 1
is used as an SFBC function, a received signal in each subcarrier
can be represented as in Equation 2. Subcarrier 1:
h.sub.1(a.sub.1+b.sub.1+c.sub.1+d.sub.1)-h.sub.2(a.sub.2+b.sub.2+c.sub.2+-
d.sub.2)* Subcarrier 2:
h.sub.1(a.sub.2+b.sub.2+c.sub.2+d.sub.2)+h.sub.2(a.sub.1+b.sub.1+c.sub.1+-
d.sub.1)* Subcarrier 3:
h.sub.3(a.sub.3+b.sub.3+c.sub.3+d.sub.3)-h.sub.4(a.sub.4+b.sub.4+c.sub.4+-
d.sub.4)* Subcarrier 4:
h.sub.3(a.sub.4+b.sub.4+c.sub.4+d.sub.4)+h.sub.4(a.sub.3+b.sub.3+c.sub.3+-
d.sub.3)* [Equation 2]
In Equation 2, h.sub.i indicates fading undergone by an i.sup.th
antenna. Preferably, subcarriers of the same antenna undergo the
same fading. A noise component added to a receiving side may be
ignored. And, a single receiving antenna preferably exists. In this
case, spread sequences obtained by a receiving side after
completion of SFBC decoding and FSTD decoding can be represented as
in Equation 3.
(|h.sub.1|.sup.2+|h.sub.2|.sup.2)(a.sub.1+b.sub.1+c.sub.1+d.sub.1),
(|h.sub.1|.sup.2+|h.sub.2|.sup.2)(a.sub.2+b.sub.2+c.sub.2+d.sub.2),
(|h.sub.3|.sup.2+h.sub.4|.sup.2)(a.sub.3+b.sub.3+c.sub.3+d.sub.3),
(|h.sub.3|.sup.2+|h.sub.4|.sup.2)(a.sub.4+b.sub.4+c.sub.4+d.sub.4)
[Equation 3]
Here, in order to separate the spread sequence obtained by the
receiving side from the signals b, c and d by despreading with a
(pseudo) orthogonal code corresponding to the signal a for example,
the wireless channel responses for the four chips is preferably the
same. However, as can be observed from Equation 3, signals
transmitted via different antenna sets by FSTD are
(|h.sub.1|.sup.2+|h.sub.2|.sup.2) and
(|h.sub.3|.sup.2+|h.sub.4|.sup.2) and provide results through
different wireless channel responses, respectively. Thus, complete
elimination of a different CDM-multiplexed signal during
dispreading is not performed.
Therefore, one embodiment of the present invention is directed to a
method of transmitting at least one spread signal in a
communication system, wherein each of at least one signal is spread
by (pseudo) orthogonal code or the like with a spreading factor
(SF), and wherein the at least one spread signal is multiplexed by
CDM and transmitted via the same antenna set. FIG. 3 is a diagram
illustrating an example for a method of applying an SFBC/FSTD
scheme to a spread signal in a communication system in accordance
with one embodiment of the present invention. In the present
embodiment, each of at least one signal is spread by (pseudo)
orthogonal code or the like with SF=4. Furthermore, the at least
one spread signal is multiplexed and transmitted by CDM, and the
multiplexed signals are transmitted via the same antenna set.
In FIG. 3, when a total of four transmitting antennas are used, a
first antenna set includes a first antenna and a second antenna. A
second antenna set includes a third antenna and a fourth antenna.
In particular, each of the first and second antenna sets is the
antenna set for performing SFBC coding, and an FSTD scheme is
applicable between the two antenna sets. According to the present
embodiment, assuming that data to be transmitted is carried by a
single OFDM symbol, the signal spread with SF=4, as shown in FIG.
3, can be transmitted via four neighbor subcarriers of one OFDM
symbol via the same SFBC-coded antenna set.
In FIG. 3(a), shown is a case where the spread signal transmitted
via the first antenna set is different from the spread signal
transmitted via the second antenna set. In FIG. 3(b), shown is a
case where the spread signal transmitted via the first antenna set
is repeatedly transmitted via the second antenna set to obtain a
4-degree transmitting antenna diversity gain.
FIG. 4 is a diagram illustrating another example for a method of
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present invention.
In the present embodiment, like the former embodiment shown in FIG.
3, each of at least one signal is spread by (pseudo) orthogonal
code or the like with SF=4. The at least one spread signal is
multiplexed and transmitted by CDM, and the multiplexed signals are
transmitted via the same antenna set.
In FIG. 4, unlike FIG. 3, when a total of four transmitting
antennas are used, a first antenna set includes a first antenna and
a third antenna. A second antenna set includes a second antenna and
a fourth antenna. Namely, compared to FIG. 3, FIG. 4 shows a case
of using a different method for constructing each antenna set but
applying the same SFBC/FSTD scheme. Here, according to the present
embodiment, the signal spread with SF=4 can be transmitted via four
neighbor subcarriers of one OFDM symbol via the same SFBC-coded
antenna set.
In FIG. 4(a), shown is a case where the spread signal transmitted
via the first antenna set is different from the spread signal
transmitted via the second antenna set. In FIG. 4(b), shown is a
case where the spread signal transmitted via the first antenna set
is repeatedly transmitted via the second antenna set to obtain a
4-degree transmitting antenna diversity gain.
FIG. 5 is a diagram illustrating an example of a method for
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with an embodiment of the present invention.
Preferably, a same signal can be repeatedly transmitted to obtain
additional diversity. Accordingly, the present embodiment relates
to a case where the same signal is repeatedly transmitted at least
twice via different subcarriers on a frequency axis, i.e., for a
period of the same time unit.
In the present embodiment, an antenna set is determined as follows.
First, after a signal has been spread with SF=4, an antenna set is
determined by a 4-subcarrier unit to enable the signal spread
according to the aforesaid embodiment to be transmitted via the
same antenna set. In this case, as mentioned in the foregoing
description, the signal is repeatedly transmitted by changing an
antenna set in case of repetitive transmission to apply the
SFBC/FSTD scheme for obtaining 4-degree transmitting antenna
diversity. According to the present embodiment, an
antenna-frequency mapping structure, to which the SFBC/FSTD scheme
for obtaining 4-degree transmitting antenna diversity gain is
applied, may be repeated by an 8-subcarrier unit.
In FIG. 5(a), shown is an example where the repetitive transmission
method is applied to the embodiment described with reference to
FIG. 3. In FIG. 5(b), shown is an example where the repetitive
transmission method is applied to the embodiment described with
reference to FIG. 4. In particular, FIG. 5(a) and FIG. 5(b) show
examples for applying the SFBC/FSTD scheme for obtaining 4-degree
transmitting antenna diversity gain using eight neighbor
subcarriers, respectively. Although FIG. 5(a) and FIG. 5(b) differ
from each other with respect to the antennas included in the first
and second antenna sets, each use the same method in applying the
present embodiment.
In accordance with the present invention, a one-time transmission
may correspond to a case where a signal having been spread with
SF=4 is CDM-multiplexed and then transmitted via four subcarriers.
Accordingly, assuming that one-time transmission is performed via
the first antenna set shown in FIG. 5(a) or 5(b), a two-time
transmission, which is the repetitive transmission of the one-time
transmission, can be carried out via the second antenna set. Thus,
it is observed that the SFBC/FSTD scheme is implemented via the
one-time transmission and the two-time transmission. In the same
manner, a three-time transmission may be carried out when the first
antenna set performs the transmission again.
FIG. 6 is a diagram illustrating another example for a method of
applying a SFBC/FSTD scheme to a spread signal in a communication
system in accordance with an embodiment of the present invention.
In FIG. 6, like the embodiment shown in FIG. 5, after a signal is
spread with SF=4, an antenna set is determined by a 4-subcarrier
unit to enable the signal spread according to the aforesaid
embodiment to be transmitted via the same antenna set. In this
case, as mentioned in the foregoing description, the signal is
repeatedly transmitted by changing an antenna set in case of
repetitive transmission to apply SFBC/FSTD for obtaining 4-degree
transmitting antenna diversity.
However, while the embodiments shown in FIG. 5 use the SFBC/FSTD
scheme through eight neighbor subcarriers, the embodiment of FIG. 6
uses subcarriers having an interval compared to a previous
transmission. Thus, frequency diversity may be obtained in addition
to 4-degree antenna diversity. Notably, it is preferable that
subcarriers through which a spread signal sequence is multiplexed
and transmitted include subcarriers that neighbor each other.
This may be explained as follows. First, a one-time transmission
may be performed using only four of eight subcarriers to which the
SFBC/FSTD scheme is applied in the embodiment shown in FIG. 5 using
a first antenna set. Subsequently, the one-time transmission is
performed using four of eight subcarriers to which the SFBC/FSTD
scheme is applied using a second antenna set. Accordingly, in order
to implement the SFBC/FSTD scheme for obtaining 4-degree
transmitting antenna diversity, an antenna set different from that
of a previous transmission is used.
In FIG. 6(a), shown is an example where a repetitive transmission
method is applied to the embodiment described with reference to
FIG. 3. In FIG. 6(b), shown is an example where a repetitive
transmission method is applied to the embodiment described with
reference to FIG. 4. Although FIG. 6(a) and FIG. 6(b) differ from
each other with respect to the antennas included in the first and
second antenna sets, each use the same method in applying the
present embodiment.
Referring to FIG. 6, compared to the method described in FIG. 5,
the embodiment of FIG. 6 may considerably save resources required
for the repetitive transmission by reducing additionally used
resources in half. Therefore, if the repetitive transmission method
according to FIG. 6 is applied, resources used for data
transmission are used more efficiently.
As described above, a method of applying an SFBC/FSTD scheme for a
single time unit according to an embodiment of the present
invention was explained. However, situations occur where a signal
may be transmitted using a plurality of time units, wherein a
single OFDM symbol may be preferably defined as a time unit in a
communication system adopting orthogonal frequency division
multiplexing. Accordingly, in accordance with an embodiment of the
present invention, a method of applying an SFBC/FSTD scheme to a
case of transmitting a signal using a plurality of OFDM symbols
will be explained.
When a signal is transmitted via a plurality of OFDM symbols,
repetitive transmission on a time axis as well as a frequency axis
is possible to obtain diversity additional to transmitting antenna
diversity. Accordingly, CDM and SFBC/FSTD schemes may be applied to
a spread signal for an ACK/NAK signal transmitted in downlink to
announce the successful/failed reception of data transmitted in
uplink.
FIG. 7 is a diagram illustrating an example of a method for
transmitting a spread signal via a plurality of OFDM symbols in
accordance with one embodiment of the present invention. Referring
to FIG. 7, each small box indicates a resource element (RE)
constructed with a single OFDM symbol and a single subcarrier.
A.sub.ij may indicate an ACK/NAK signal multiplexed by CDM, wherein
"i" indicates an index of a signal spread and then multiplexed, and
"j" indicates an ACK/NAK channel index of the multiplexed ACK/NAK
signal. In this case, an ACK/NAK channel indicates a set of
multiplexed ACK/NAK signals. A plurality of ACK/NAK channels may
exist according to necessity and resource situation of each system.
However, for clarity and convenience of description, a single
ACK/NAK channel exists in FIG. 7.
In FIG. 7(a), shown is an example where a multiplexed ACK/NAK
signal is transmitted via a single OFDM symbol. Referring to FIG.
7(a), four ACK/NAK signals are spread by a spreading factor equal
to four (SF=4) for a single OFDM symbol, multiplexed by CDM, and
then transmitted via four neighbor subcarriers. Because a single
OFDM symbol is used for the ACK/NAK signal transmission, diversity
gain on a time axis may not be obtained. However, four repetitive
transmissions of the ACK/NAK signal multiplexed by CDM may be
carried out along a frequency axis. Hence, the four-time repetitive
transmission exemplifies repetition to obtain diversity. Notably, a
repetition count may vary according to a channel status and/or a
resource status of a system.
In FIG. 7(b), shown is an example where a multiplexed ACK/NAK
signal is transmitted via a plurality of OFDM symbols. Referring to
FIG. 7(b), four ACK/NAK signals are spread by a spreading factor
SF=4 for two OFDM symbols each, multiplexed by CDM, and then
transmitted via four neighbor subcarriers. Namely, in case that
OFDM symbols for ACK/NAK signal transmission increase, the ACK/NAK
signal may be repetitively transmitted using a single OFDM symbol
for the increased OFDM symbols as it is. However, when the ACK/NAK
signal is repetitively transmitted for a second OFDM symbol,
transmission is performed to maximize use of subcarriers that are
not overlapped with former subcarriers used for the first OFDM
symbol. This is preferable considering a frequency diversity
effect.
In FIG. 7(b), shown is a case where the number of ACK/NAK signals
transmittable despite the increased number of OFDM symbols is equal
to the case where a single OFDM symbol is used. Previously, an
ACK/NAK signal was transmitted repeatedly only on a frequency axis
when using a single OFDM symbol. However, in accordance with the
present embodiment, more time-frequency resources may be used for
transmitting the same number of ACK/NAK signals as in the single
OFDM symbol case by substantially incrementing the repetition count
of time-frequency. Here, because OFDM symbols used for the ACK/NAK
transmission are increased, more signal power used for the ACK/NAK
transmission can be allocated. Hence, the ACK/NAK signal may be
transmitted to a cell having a wider area.
In FIG. 7(c), shown is another example where multiplexed ACK/NAK
signals are transmitted via a plurality of OFDM symbols. Referring
to FIG. 7(c), when the number of OFDM symbols for ACK/NAK signal
transmission is set at 2, the transmission may be carried out by
reducing the frequency-axis repetition count of the ACK/NAK signal
multiplexed by CDM. Thus, by decreasing the repetition count to
facilitate transmission when the number of OFDM symbols is set at
2, resources are efficiently utilized.
Compared with the transmission method shown in FIG. 7(b), four
time-frequency axis transmission repetitions of the ACK/NAK signal
are reduced to two transmission repetitions in FIG. 7(c). However,
because the number of OFDM symbols used for the ACK/NAK signal
transmission is incremented, the transmission method shown in FIG.
7(c) is similar to the method shown in FIG. 7(a), where a single
OFDM symbol is used, because four time-frequency resource areas are
available in both the methods shown in FIGS. 7(a) and 7(c).
Furthermore, compared to the transmission method shown in FIG.
7(b), the method shown in FIG. 7(c) may reduce the signal power for
ACK/NAK channel transmission because the number of time-frequency
resource areas used for a single ACK/NAK channel transmission is
reduced. Moreover, because the ACK/NAK channel is transmitted
across the time-frequency areas, per-symbol transmission power
allocation may be performed more efficiently than transmission over
a single OFDM symbol only.
In case that ACK/NAK signals are repetitively transmitted in the
same structure for all OFDM symbols to simplify a system's
scheduling operation, such as when the time-frequency resources
shown in FIG. 7(b) are used for example, different ACK/NAK channels
may be transmitted. In particular, because double ACK/NAK channels
are transmittable, more efficient resource use is achieved.
As described above, a spreading factor for multiplexing a plurality
of ACK/NAK signals, a repetition count in time-frequency domain and
the number of OFDM symbols for ACK/NAK signal transmission, which
are explained with reference to FIG. 7, are exemplarily provided
for a more accurate description of the present invention. It is
understood that different spreading factors, different repetition
counts and various OFDM symbol numbers are applicable to the
present invention. Moreover, the embodiments shown in FIG. 7 may
relate to using a single transmitting antenna that does not use
transmitting antenna diversity, but may also be applicable to a
2-transmitting antenna diversity method, 4-transmitting antenna
diversity method, and the like.
FIG. 8 is a diagram illustrating an example of a method for
transmitting spread signals via a plurality of OFDM symbols in
accordance with one embodiment of the present invention, in which
an SFBC/FSTD scheme is applied to the spread signal. Referring to
FIG. 8, a 4-degree transmitting antenna diversity method using a
total of four transmitting antennas is implemented. Here, a single
ACK/NAK channel exists for clarity and convenience of
description.
In FIG. 8(a), an SFBC/FSTD scheme is applied to a spread signal
using four transmitting antennas, and the signal is transmitted for
a plurality of OFDM symbols. Furthermore, four ACK/NAK signals are
spread with a spreading factor SF=4 for each of two OFDM symbols,
multiplexed by CDM, and then transmitted via four neighbor
subcarriers. Preferably, when OFDM symbols for ACK/NAK signal
transmission increase, the ACK/NAK signal may be repetitively
transmitted using a single OFDM symbol for the increased OFDM
symbols as it is. Notably, this process is similar to the process
described with reference to FIG. 7(b).
However, when a repetitive transmission is performed for a second
OFDM symbol, it is carried out using an antenna set different from
an antenna set used for a first OFDM symbol. For example, if a
transmission for a first OFDM symbol is performed using a first
antenna set including a first antenna and a third antenna, a
transmission for a second OFDM symbol can be performed using a
second antenna set including a second antenna and a fourth antenna.
Accordingly, the transmission for the second OFDM symbol is carried
out by maximizing use of subcarriers not overlapped with former
subcarriers used for the first OFDM symbol. This is preferable to
achieve a frequency diversity effect.
In FIG. 8(b), shown is another example of applying an SFBC/FSTD
scheme to a spread signal using four transmitting antennas and
transmitting the signal for a plurality of OFDM symbols in
accordance with one embodiment of the present invention. Referring
to FIG. 8(b), when the number of OFDM symbols for ACK/NAK signal
transmission is set to 2, the signal may be transmitted by reducing
a frequency-axis repetition count of the ACK/NAK signal multiplexed
by CDM. Notably, this process is similar to the method described
with reference to FIG. 7(c). However, when repetitive transmission
is carried out for a second OFDM symbol, the transmission will be
performed using an antenna set different from the antenna set used
for the first OFDM symbol.
FIG. 9 is a diagram illustrating an example for a method of
applying an SFBC/FSTD scheme to a spread signal in a communication
system in accordance with one embodiment of the present invention.
Referring to FIG. 9, when a total of four transmitting antennas are
used, a first antenna set includes a first antenna and second
antenna, and a second antenna set includes a third antenna and
fourth antenna. Preferably, each of the first and second antenna
sets is an antenna set for performing SFBC coding and an FSTD
scheme applicable between the two antenna sets. According to the
present embodiment, if data is transmitted for a single OFDM
symbol, the signal spread with SF=2, as shown in FIG. 9, can be
transmitted via two neighbor subcarriers of one OFDM symbol via the
same SFBC-coded antenna set.
In FIG. 9(a), shown is a case where the spread signal transmitted
via the first antenna set is different from the spread signal
transmitted via the second antenna set. In FIG. 9(b), shown is a
case where the spread signal transmitted via the first antenna set
is repeatedly transmitted via the second antenna set to obtain a
4-degree transmitting antenna diversity gain.
Accordingly, with regard to FIG. 9, a single signal may be spread
with SF=2. Thus, the same structure as applying an SFBC/FSTD scheme
by 4-subcarrier unit for a CDM-multiplexed signal may be used, but
without considering spreading as in FIG. 1.
FIG. 10 is a diagram for illustrating another example of a method
for applying an SFBC/FSTD scheme to spread signals in a
communication system in accordance with one embodiment of the
present invention. In the embodiment shown in FIG. 10, like the
former embodiment shown in FIG. 9, at least one or more signals are
spread by (pseudo) orthogonal code or the like with SF=2. The at
least one or more spread signals are also multiplexed and
transmitted by CDM. Here, the multiplexed signals are transmitted
via the same antenna set.
In FIG. 10, unlike FIG. 9, when a total of four transmitting
antennas are used, a first antenna set includes a first antenna and
third antenna, and a second antenna set includes a second antenna
and fourth antenna. Thus, compared to FIG. 9, FIG. 10 illustrates
use of a different method for constructing each antenna set but
applies the same SFBC/FSTD scheme. In accordance with the present
embodiment, the signal spread with SF=2 may be transmitted via two
neighbor subcarriers of one OFDM symbol via the same SFBC-coded
antenna set.
In FIG. 10(a), shown is a case where the spread signal transmitted
via the first antenna set is different from the spread signal
transmitted via the second antenna set. In FIG. 10(b), shown is a
case where the spread signal transmitted via the first antenna set
is repeatedly transmitted via the second antenna set to obtain a
4-degree transmitting antenna diversity gain.
Accordingly, with regard to FIG. 10, a single signal may be spread
by SF=2. Thus, the same structure as applying SFBC/FSTD by
4-subcarrier unit for a CDM-multiplexed signal may be used without
considering spreading as in FIG. 1.
FIG. 11 is a diagram illustrating another example of a method for
applying an SFBC/FSTD scheme to spread signals in a communication
system in accordance with one embodiment of the present invention.
In accordance with the present invention, a same signal can be
repeatedly transmitted to obtain additional diversity. In
particular, the same signal may be repeatedly transmitted at least
once via different subcarriers on a frequency axis, i.e., for a
period of the same time unit.
Referring to FIG. 11, an antenna set is determined as follows in
accordance with the present invention. After a signal has been
spread with SF=2, a plurality of the spread signals are
multiplexed. An antenna set is then determined by 2-subcarrier unit
to enable the spread signal to be transmitted via the same antenna
set. In this case, the signal is repeatedly transmitted by changing
an antenna set in case of repetitive transmission to apply the
SFBC/FSTD scheme for obtaining the 4-degree transmitting antenna
diversity. Accordingly, an antenna-frequency mapping structure, to
which the SFBC/FSTD scheme for obtaining 4-degree transmitting
antenna diversity gain is applied, is repeated by 4-subcarrier
unit.
In FIG. 11(a), shown is an example where the repetitive
transmission method is applied to the embodiment described with
reference to FIG. 9. In FIG. 11(b), shown is an example where the
repetitive transmission method is applied to the embodiment
described with reference to FIG. 10. In particular, FIG. 11(a) and
FIG. 11(b) illustrate examples for applying the SFBC/FSTD scheme
using four neighbor subcarriers, respectively. Notably, FIGS. 11(a)
and 11(b) differ from each other with respect to the antennas
included in the first and second antenna sets, but use the same
method in applying the described embodiment.
FIG. 12 is a diagram illustrating another example of a method for
applying an SFBC/FSTD scheme to spread signals in a communication
system in accordance with one embodiment of the present invention.
In FIG. 12, like the embodiment shown in FIG. 11, after a plurality
of signals spread with SF=2 have been multiplexed, an antenna set
is determined by 2-subcarrier unit to enable the spread signals to
be transmitted via the same antenna set. Here, the signal may be
repeatedly transmitted by changing an antenna set in case of
repetitive transmission to apply the SFBC/FSTD scheme for obtaining
the 4-degree transmitting antenna diversity.
However, unlike the embodiment shown in FIG. 11 wherein the
SFBC/FSTD scheme is applied through the four neighbor subcarriers,
the embodiment of FIG. 12 uses a subcarrier having a prescribed
interval by comparing a subcarrier used for repetitive transmission
to that of a previous transmission. Notably, it is preferable that
subcarriers through which a spread signal sequence is multiplexed
and transmitted include subcarriers that neighbor each other.
In FIG. 12(a), shown is an example where a repetitive transmission
method is applied to the embodiment described with reference to
FIG. 9. In FIG. 12(b), shown is an example where a repetitive
transmission method is applied to the embodiment described with
reference to FIG. 10. Notably, FIGS. 12(a) and 12(b) differ from
each other with respect to the antennas included in the first and
second antenna sets but use the same method in applying the
described embodiment.
Accordingly, the embodiment of FIG. 12 may be described as follows.
First, a one-time transmission is first performed using two of four
subcarriers to which an SFBC/FSTD scheme is applied. The one-time
transmission is then carried out using two of four subcarriers to
which a next SFBC/FSTD scheme is applied. In this case, an antenna
set different from that of a previous transmission is used to
implement the SFBC/FSTD scheme.
FIG. 13 is a diagram illustrating an example of a method for
applying an SFBC/FSTD scheme to at least one spread signal in a
communication system in accordance with one embodiment of the
present invention. Preferably, if an antenna-frequency mapping
structure according to the SFBC/FSTD transmission scheme shown in
FIG. 1 is maintained collectively for each OFDM symbol or subframe
on a system, then the rest of an SFBC antenna set unused in the
SFBC/FSTD scheme of FIG. 12 may be used for another data
transmission.
Referring to FIG. 13, the same antenna-frequency mapping structure
in the SFBC/FSTD scheme for obtaining 4-degree transmitting antenna
diversity gain by the 4-subcarrier unit (described with reference
to FIG. 1) is used. Accordingly, two different multiplexed signals
may be transmitted using this structure. Here, each of the
multiplexed signals is a multiplexed signal spread by SF=2, and can
be transmitted through two subcarriers.
As applied, in the SFBC/FSTD transmission scheme for transmitting a
random multiplexed signal generated from multiplexing a plurality
of spread data signals, a second antenna set other than a first
antenna set to be SFBC-coded can be used to transmit another
multiplexed signal. Moreover, by repeatedly transmitting the
multiplexed signals via the first and second antenna sets, the
multiplexed signals may respectively be transmitted through the
different antenna sets. Hence, a 4-degree transmitting antenna
diversity effect may be obtained.
For example, a first multiplexed signal is transmitted via first
antenna set and a second multiplexed signal is transmitted via
second antenna set. In case of a repetitive transmission, mapping
between a multiplexed signal and an antenna is changed.
Accordingly, the second multiplexed signal will be transmitted via
the first antenna set, while the first multiplexed signal is
transmitted via the second antenna set. In case of a next
repetitive transmission, the mapping between the multiplexed signal
and the antenna is changed again to perform the corresponding
transmission. Thus, the first multiplexed signal will again be
transmitted via first antenna set and the second multiplexed signal
will again be transmitted via second antenna set. Accordingly, if
transmission is performed in the above-mentioned manner, resources
are efficiently used. Moreover, the antenna-frequency mapping
structure in the SFBC/FSTD scheme described with reference to FIG.
1 will be maintained.
In the example above, the signal spread by SF=2 is transmitted via
a single OFDM symbol only. If so, repetition on a frequency axis is
possible to obtain additional frequency diversity. However, using a
single OFDM symbol is merely exemplary for illustrating the present
invention. As mentioned in the foregoing description of SF=4, the
present embodiment is applicable to a case of using several OFDM
symbols.
When transmitting via several OFDM symbols, repetition on a time
axis as well as a frequency axis is applicable to obtain diversity
in addition to transmitting antenna diversity. The above
embodiments are provided to explain applications of the present
invention and are also applicable to a system using an SFBC/FSTD
transmission diversity method regardless of various spreading
factors (SF), various OFDM symbols numbers and repetition counts on
time and frequency axes.
FIG. 14 is a diagram illustrating an example of a method for
transmitting a spread signal in a mobile communication system in
accordance with one embodiment of the present invention. Referring
to FIG. 14, a transmitting end spreads a signal using a plurality
of spreading codes (S1402). The plurality of spreading codes have a
spreading factor of 4. The transmitting end codes the spread signal
for multiple antenna transmission (S1404). The transmitting end
multiplexes the coded spread signal by code division multiplexing
per each antenna (S1406). The transmitting end transmits the
multiplexed signal via four neighboring frequency resources of one
OFDM symbol of a first antenna set consisting of two antennas
(S1408). The transmitting end transmits the same multiplexed signal
via four neighboring frequency resources of one OFDM symbol of a
second antenna set consisting of two antennas (S1410). The
multiplexed signal transmitted via the first antenna set and the
multiplexed signal transmitted via the second antenna set are
transmitted via respectively different OFDM symbols. The
multiplexed signal transmitted via the first antenna set and the
multiplexed signal transmitted via the second antenna set are
separated from each other in a frequency domain.
FIG. 15 is a diagram illustrating an example of a method for
receiving a spread signal in a mobile communication system in
accordance with one embodiment of the present invention. Referring
to FIG. 15, a receiving end receives multiplexed signal via four
neighboring frequency resources of one OFDM symbol, the multiplexed
signal being transmitted from a first antenna set consisting of two
antennas of a transmitting end (S1502). The receiving end receives
the same multiplexed signal via four neighboring frequency
resources of one OFDM symbol, the same multiplexed signal being
transmitted from a second antenna set consisting of two antennas of
the transmitting end (S1504). The multiplexed signal transmitted
via the first antenna set and the multiplexed signal transmitted
via the second antenna set are transmitted from the transmitting
end via respectively different OFDM symbols. The multiplexed signal
is obtained at the transmitting end from a coded spread signal
using code division multiplexing per each antenna. The coded spread
signal is obtained at the transmitting end by coding a spread
signal between the two antennas in the first antenna set and the
second antenna set.
Embodiments of the present invention can be implemented by various
means, e.g., hardware, firmware, software, and any combination
thereof. In case of the implementation by hardware, a method of
transmitting a spread signal in a communication system according to
one embodiment of the present invention can be implemented by at
least one of application specific integrated circuits (ASICs),
digital signal processors (DSPs), digital signal processing devices
(DSPDs), programmable logic devices (PLDs), field programmable gate
arrays (FPGAs), a processor, a controller, a microcontroller, a
microprocessor, etc.
In case of implementation by firmware or software, a method of
transmitting a spread signal in a communication system according to
one embodiment of the present invention can be implemented by a
module, procedure, function and the like capable of performing the
above mentioned functions or operations. Software code is stored in
a memory unit and can be driven by a processor. The memory unit is
provided within or outside the processor to exchange data with the
processor by various means known in public.
FIG. 16 is a diagram illustrating an example of a base station and
a user equipment in a mobile communication system in accordance
with one embodiment of the present invention. Referring to FIG. 16,
the base station (BS) (1600) includes one or more antennas (1602),
a radio frequency unit (1604), and a processor (1606) and the user
equipment (UE) (1610) includes an antenna (1612), a radio frequency
unit (1614), and a processor (1616).
The foregoing embodiments and advantages are merely exemplary and
are not to be construed as limiting the present invention. The
present teaching can be readily applied to other types of
apparatuses. The description of the present invention is intended
to be illustrative, and not to limit the scope of the claims. Many
alternatives, modifications, and variations will be apparent to
those skilled in the art. In the claims, means-plus-function
clauses are intended to cover the structure described herein as
performing the recited function and not only structural equivalents
but also equivalent structures.
* * * * *